That big timeline change is coming today, but it’s not as Twitter-shattering as first reported.

Over the weekend, BuzzFeed reported that Twitter was going to an algorithm-based timeline, where a computer picks the tweets a user sees, instead of everything showing up in reverse chronological order, as it happens. There was mass panic — #RIPTwitter was trending — and users feared the messaging service would just become another Facebook.

Don’t miss anything
“We’re bringing tweets people care about the most to the top of the timeline,” Ranadive said. It’s an extension of a feature Twitter already had called “While You Were Away.” The new version will surface about 12 tweets atop a user’s timeline before returning to reverse chronological order, in which tweets appear as they are posted in real time.

But do I have to look at this?
No. “Customers will have a choice,” Ranadive said. In fact, users will be asked to opt-in to the timeline today, and they will be able to opt-out any time by changing their settings.

How does it know what I like?
Twitter’s algorithm will surface tweets based on accounts you follow and your interests. Twitter is looking at billions of tweets and at how you’re interacting with them to determine which to bring to the top. So, if you’re interested in Fuzzy Emergency, you’ll see cats. If it’s football, you’ll see the NFL, Ranadive said.

Brand effect
In the tests, reach and engagement increased on brands’ posts, Ranadive said. Typically, brands see a low engagement rate on unpaid Twitter posts, so it makes sense an algorithm could help increase visibility. Twitter did not reveal the engagement rate seen in the test of the new timeline offering. Sponsored posts will continue to appear in the mix, and Twitter also has a new 24-hour video ad that could show at the top of the page, offered as a premium video buy for brands.